1. Field of the Invention
The present invention relates to image forming apparatuses, such as copiers, printers, and facsimiles, and methods for detecting the fullness of waste-toner containers.
2. Description of the Related Art
In general, electrophotographic image forming apparatuses, which use toner, perform image formation (printing) by forming a toner image on a photosensitive drum, transferring the toner image to a recording medium such as a sheet, and fixing the image on the sheet. The toner that was not transferred to the recording medium (waste toner) is collected. A waste-toner container for storing the waste toner is provided in the image forming apparatus.
If the waste toner continues to be sent to the waste-toner container after the container is full, the member used to convey the waste toner (for example, a conveying screw or a conveying tube) can be damaged or the waste toner, that is unable to be stored in the container, can spill during the replacement of the waste-toner container, which may cause a problem in that the inside of the image forming apparatus becomes dirty.
Devices for detecting the fullness of a waste-toner container are known. More specifically, an image forming apparatus is known, which includes a waste toner collection bottle for storing waste toner, a movable shutter that moves to prevent the waste toner from leaking from a toner discharge port when the waste toner collection bottle is not attached to the image forming apparatus, bottle detection means for detecting the presence of the waste toner collection bottle, and toner fullness detection means that detects if the waste toner collection bottle is full with waste toner. The image forming apparatus has a projection that protrudes below the movable shutter and can be detected by the toner fullness detection means, and is configured such that the toner fullness detection means also serves as the bottle detection means. With this design, cost reductions are sought.
More specifically, by detecting whether or not the waste-toner container is filled to a predetermined level with the waste toner using a light sensor, the fullness of the waste-toner container can be detected. In general, when the waste-toner container is determined to be full, the image forming apparatus is put into a non-printable state to prevent a situation where printing is continued and waste toner continues to be fed despite the fact that the waste-toner container is full (for example, in the case during printing, the printing is aborted or no new printing job is started).
However, because the waste toner is in powder form, a cone-shaped pile of the waste toner deposited in the waste-toner container may collapse because of: vibrations applied to the image forming apparatus during printing; new waste toner that is added to the waste-toner container; weight of the waste toner and the like. In other words, the top portion of the waste toner can shift and the level of the waste toner may change. As a result, the waste toner may not block the optical path of the light sensor, which allows the image forming apparatus to determine that the waste-toner container is not full or the waste-toner container has been replaced, and to voluntarily recover from a non-printable state to the printable state (in the case during continuous printing, printing may be repeatedly aborted and restarted). This leads to a problem in that a user may misconceive that the image forming apparatus is malfunctioning or failed. The image forming apparatus set forth above does not have a countermeasure to be taken when the deposited pile of the waste toner collapses, and thus, is unable to solve the above-described problem.
Cost is reduced in the image forming apparatus by making a single sensor perform a plurality of detections. However, with the image forming apparatus, if the cover for the replacement of the waste-toner container is opened, the fullness of the waste-toner container cannot be accurately detected because of outside light, such as illumination light or solar light. Accordingly, the image forming apparatus requires a switch, or the like, to detect whether or not the cover is open, and thus, the reduction in production costs is insufficient. Furthermore, in the image forming apparatus, the detection of the fullness of the waste-toner container and the detection of the attachment of the bottle are both performed using blocking of light incident on a light-receiving portion. However, because it is impossible to clearly distinguish the situation where the waste-toner container is full and the situation where the bottle is not attached, detection performance is insufficient.